Thiazolemethine dyes

ABSTRACT

Methine dyes of the formula I ##STR1## where R is hydrogen, unsubstituted or substituted C 1  -C 10  -alkyl or unsubstituted or substituted phenyl, 
     X is nitrogen or a radical of the formula CQ 1 , CH═CQ 1  --CH, CH═CH--CH═CH--CH, ##STR2## where Q 1  is hydrogen, C 1  -C 4  -alkyl, chlorine or bromine and Q 2  is hydrogen or C 1  -C 4  -alkyl, and 
     Y is a radical of the aniline, aminonaphthalene, indole, aminoquinoline, aminothiazole or aminothiophene series, 
     the use thereof in nonlinear optics, and novel thiazole derivatives.

This is a 371 of PCT/EP95/01348 filed Apr. 12, 1995.

The present invention relates to novel methine dyes of the formula I##STR3## where R is hydrogen, unsubstituted or substituted C₁ -C₁₀-alkyl or unsubstituted or substituted phenyl,

X is nitrogen or a radical of the formula CQ¹, CH═CQ¹ --CH,CH═CH--CH═CH--CH, ##STR4## where Q¹ is hydrogen, C₁ -C₄ -alkyl, chlorineor bromine and Q² is hydrogen or C₁ -C₄ -alkyl, and

Y is a radical of the aniline, aminonaphthalene, indole, aminoquinoline,aminothiazole or aminothiophene series,

with the proviso that X is not CH when R is phenyl and Y is a radical ofthe aniline series, to the use thereof in nonlinear optics and to novelthiazole derivatives.

U.S. Pat. No. 5,364,919 discloses the use of methine dyes in polymericnonlinear optical systems.

It is an object of the present invention to provide novel methine dyeswhich are advantageously suitable for use in polymeric nonlinear opticalsystems. In particular, dyes of this type ought to have largehyperpolarizability values, good thermal stability, good compatibilitywith the polymers used in nonlinear optical systems and goodfilm-forming properties with copolymers.

We have found that this object is achieved by the methine dyes of theformula I defined at the outset.

Examples of suitable radicals Y are those of the formulae IIa to IIi##STR5## where n is 0 or 1,

Z¹ is hydrogen, C₁ -C₁₀ -alkyl which may be interrupted by 1 or 2 oxygenatoms in ether functionalities, C₁ -C₄ -alkoxy, especially methoxy orethoxy, C₁ -C₄ -alkylsulfonylamino, C₁ -C₄ -mono- ordialkylaminosulfonylamino or --NHCOZ⁷ or --NHCO₂ Z⁷ where Z⁷ is phenyl,benzyl, tolyl or C₁ -C₁₀ -alkyl which may be interrupted by 1 or 2oxygen atoms in ether functionalities,

Z² is hydrogen, C₁ -C₄ -alkyl, especially methyl, or C₁ -C₄ -alkoxy,especially methoxy or ethoxy,

Z³ and Z⁴ are identical or different and are each, independently of oneanother, hydrogen, C₁ -C₁₀ -alkyl which may be substituted and may beinterrupted by 1 or 2 oxygen atoms in ether functionalities, C₃ -C₄-alkenyl, C₅ -C₇ -cycloalkyl, phenyl or tolyl or together with thenitrogen atom connecting them a 5- or 6-membered saturated heterocyclicradical which may contain further heteroatoms,

Z⁵ is halogen or unsubstituted or substituted phenyl and

Z⁶ is hydrogen, halogen, C₁ -C₁₀ -alkyl, unsubstituted or substitutedphenyl, unsubstituted or substituted benzyl, cyclohexyl, thienyl,hydroxyl or C₁ -C₁₀ -monoalkylamino.

All the alkyl and alkenyl groups occurring in the abovementionedformulae may be either straight-chain or branched.

Examples of suitable substituents for substituted alkyl groups in theabovementioned formulae are, unless stated otherwise, cyano, phenyl,tolyl, hydroxyl, C₁ -C₆ -alkanoyloxy, acryloyloxy, methacryloyloxy, C₁-C₄ -alkoxycarbonyl, C₁ -C₄ -alkylaminocarbonyloxy or C₁ -C₄-alkoxycarbonyloxy, it being possible in the latter case for the alkoxygroup to be substituted by phenyl or C₁ -C₄ -alkoxy. As a rule, thealkyl groups then have 1 or 2 substituents.

Examples of suitable substituents for substituted phenyl groups in theabovementioned formulae are halogen, C₁ -C₄ -alkyl, C₃ -C₇ -cycloalkyl,hydroxyl, C₁ -C₄ -alkoxy, C₁ -C₆ -alkanoyloxy, acryloyloxy ormethacryloyloxy. As a rule, the phenyl groups then have 1 to 3substituents.

Examples of suitable Q¹, Q², R, Z¹, Z², Z³, Z⁴, Z⁶ and Z⁷ radicals aremethyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl ortert-butyl.

Further examples of R, Z¹, Z³, Z⁴, Z⁶ and Z⁷ are pentyl, isopentyl,neopentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, octyl,2-ethylhexyl, isooctyl, nonyl, isononyl, decyl or isodecyl (the namesisooctyl, isononyl and isodecyl are trivial names derived from thealcohols obtained by oxo synthesis, cf. Ullmann's Encyclopedia ofIndustrial Chemistry, 5th Edition, Vol. A1, pages 290 to 293, and Vol. A10, pages 284 and 285).

Further examples of Z¹, Z³, Z⁴ and Z⁷ are 2-methoxyethyl, 2-ethoxyethyl,2-propoxyethyl, 2-isopropoxyethyl, 2-butoxyethyl, 2- or 3-methoxypropyl,2- or 3-ethoxypropyl, 2- or 3-propoxypropyl, 2- or 3-butoxypropyl, 2- or4-methoxybutyl, 2- or 4-ethoxybutyl, 2- or 4-butoxybutyl,3,6-dioxaheptyl, 3,6-dioxaoctyl, 4,8-dioxanonyl, 3,7-dioxaoctyl,3,7-dioxanonyl, 4,7-dioxaoctyl, 4,7-dioxanonyl or 4,8-dioxadecyl.

Further examples of R, Z³ and Z⁴ are benzyl, 2-methylbenzyl or 1- or2-phenylethyl.

Further examples of R and Z⁶, and examples Z⁵, are phenyl, 2-, 3- or4-methylphenyl, 2-, 3- or 4-ethylphenyl, 2-, 3- or 4-propylphenyl, 2-,3- or 4-isopropylphenyl, 2-, 3- or 4-butylphenyl, 2,4-dimethylphenyl,2-, 3- or 4-cyclopropylphenyl, 2-, 3- or 4-cyclobutylphenyl, 2-, 3- or4-cyclopentylphenyl, 2-, 3- or 4-cyclohexylphenyl, 2-, 3- or4-cycloheptylphenyl, 2-, 3- or 4-hydroxyphenyl, 2-, 3- or4-methoxyphenyl, 2-, 3- or 4-ethoxyphenyl, 2-, 3- or 4-isobutoxyphenyl,2,4-dimethoxyphenyl, 2-, 3- or 4-chlorophenyl, 2,4-dichlorpphenyl, 2-,3- or 4-acryloyloxyphenyl, 2,4-bis(acryloyloxy)phenyl, 2-, 3- or4-methacryloyloxyphenyl, 2,4-bis(methacryloyloxy)phenyl, 2-, 3- or4-hydroxyphenyl, 2-, 3- or 4-formyloxyphenyl, 2-, 3- or4-acetyloxyphenyl, 2-, 3- or 4-propionyloxyphenyl, 2-, 3- or4-butyryloxyphenyl or 2-, 3- or 4-isobutyryloxyphenyl.

Further examples of R, Z³ and Z⁴ are 2-cyanoethyl, 2- or 3-cyanopropyl,2-acetyloxyethyl, 2- or 3-acetyloxypropyl, 2-isobutyryloxyethyl, 2- or3-isobutyryloxypropyl, 2-methoxycarbonylethyl, 2- or3-methoxycarbonylpropyl, 2-ethoxycarbonylethyl, 2- or3-ethoxycarbonylpropyl, 2-dimethylaminocarbonyloxyethyl,2-diethylaminocarbonyloxyethyl, 2- or 3-dimethylaminocarbonyloxypropyl,2- or 3-diethylaminocarbonyloxypropyl, 2-methoxycarbonyloxyethyl, 2- or3-methoxycarbonyloxypropyl, 2-ethoxycarbonyloxyethyl, 2- or3-ethoxycarbonyloxypropyl, 2-butoxycarbonyloxyethyl, 2- or3-butoxycarbonyloxypropyl, 2-(2-phenylethoxycarbonyloxy)ethyl, 2- or3-(2-phenylethoxycarbonyloxy)propyl, 2-(2-ethoxyethoxycarbonyloxy)ethyl,2- or 3-(2-ethoxyethoxycarbonyloxy)propyl, 2-hydroxyethyl, 2- or3-hydroxypropyl, 2- or 4-hydroxybutyl, 5-hydroxypentyl, 6-hydroxyhexyl,7-hydroxyheptyl, 8-hydroxyoctyl, 2-acryloyloxyethyl,2-methacryl-oyloxyethyl, 2- or 3-acryloyloxypropyl, 2- or3-methacryloyloxypropyl, 2- or 4-acryloyloxybutyl, 2- or4-methacryloyloxybutyl, 5-acryloyloxypentyl, 5-methacryloyloxypentyl,6-acryloyloxyhexyl, 6-methacryloyloxyhexyl, 7-acryloyloxyheptyl,7-methacryloyloxyheptyl, 8-acryloyloxyoctyl, 8-methacryloyloxyoctyl,cyclopentyl, cyclohexyl, cycloheptyl, allyl or methallyl.

Further examples of Z¹ and Z² are methoxy, ethoxy, propoxy, isopropoxy,butoxy, isobutoxy or sec-butoxy.

Examples of Z¹ radicals are methylsulfonylamino, ethylsulfonylamino,propylsulfonylamino, isopropylsulfonylamino, butylsulfonylamino, mono-or dimethylaminosulfonylamino, mono- or diethylaminosulfonylamino, mono-or dipropylaminosulfonylamino, mono- or diisopropylaminosulfonylamino,mono- or dibutylaminosulfonylamino or(N-methyl-N-ethylaminosulfonyl)amino.

Further examples of Z⁵ and Z⁶ radicals are fluorine, chlorine orbromine.

Further examples of Z⁶ radicals are benzyl, 2-methylbenzyl,2,4-dimethylbenzyl, 2-methoxybenzyl, 2,4-dimethoxybenzyl, methylamino,ethylamino, propylamino, isopropylamino, butylamino, pentylamino,hexylamino, heptylamino, octylamino or 2-ethylhexylamino.

When Z³ and Z⁴ together with the nitrogen atom connecting them are a 5-or 6-membered saturated heterocyclic radical which may have furtherheteroatoms, possible examples thereof are pyrrolidinyl, piperidinyl,morpholinyl, piperazinyl or N-(C₁ -C₄ -alkyl)piperazinyl.

Preferred methine dyes of the formula I are those where Y is derivedfrom a component of the aniline, aminonaphthalene or aminoquinolineseries, especially radicals of the formulae IIa to IIe.

Preference is further given to methine dyes of the formula I where X isnitrogen or a radical of the formula CH, CH═CH--CH or CH═CH--CH═CH--CH.

Preference is further given to methine dyes of the formula I where R isC₁ -C₆ -alkyl or unsubstituted or hydroxyl-, acryloyloxy- ormethacryloyloxy-substituted phenyl.

Particularly interesting dyes of the formula I are those where Y isderived from a component of the aniline series, especially radicals ofthe formula IIa.

Particularly important dyes of the formula I are those where Y is aradical of the formula IIa, IIb or IIc, and especially worth mentioningis a radical of the formula IIa.

Further particularly important dyes of the formula I are those whichhave at least one polymerizable group, in particular an acryloyloxy ormethacryloyloxy radical.

The present invention further provides thiazole derivatives of theformula IVa ##STR6## where W is hydrogen, C₁ -C₆ -alkanoyl, acryloyl ormethacryloyl.

The methine dyes of the formula I can be prepared by conventionalmethods.

For example, an aldehyde of the formula III

    Y--L═O                                                 (III),

where Y has the abovementioned meaning and L is a radical of the formulaCQ¹, CH═CQ¹ --CH, CH═CH--CH═CH--CH, ##STR7## where Q¹ and Q² each havethe abovementioned meanings, can be reacted with a thiazole of theformula IV ##STR8## where R has the abovementioned meaning.

Those methine dyes of the formula I where X is nitrogen can be obtainedfor example by condensation of nitroso compounds of the formula V

    Y--NO                                                      (V),

where Y is as defined above, or by oxidative coupling of amino compoundsof the formula VI

    Y--NH.sup.2                                                (VI),

where Y is as defined above, with a thiazole IV.

The compounds of the formula IV, which include the thiazole derivativesof the formula Ira, are obtainable by reaction of ketones of the formulaVII

    Hal--CH.sub.2 --CO--R                                      (VII),

where Hal is halogen and R is as defined above, with ammoniumthiocyanate and malononitrile. Further details are also discernible fromthe Examples.

Those compounds of the formula I or IV where R is hydroxyphenyl(W=hydrogen in the formula IVa) can then be obtained for example byaqueous alkaline hydrolysis of those compounds in which R isalkanoyloxyphenyl (W=C₁ -C₆ -alkanoyl in the formula IVa).

The methine dyes of the formula I are advantageously suitable for use innonlinear optics.

The compounds according to the invention are thermally stable and haveparticularly large molecular hyperpolarizability values (β₀). Inaddition, the dyes are very compatible with the polymers used innonlinear optical systems and have good film-forming properties incopolymers.

The molecular hyperpolarizability can be determined, for example, by thesolvatochromism method (see, for example, Z. Naturforschung 20a (1965)1441-1471, or J. Org. Chem. 54 (1989) 3775-3778). This entailsdetermination of the position of the absorption band of a compound invarious solvents, eg. in dioxane and dimethyl sulfoxide. The shift inthe absorption band is then directly proportional to the value of β₀,ie. compounds with a large solvatochromic shift have a large molecularhyperpolarizability and are therefore very suitable for use in nonlinearoptical systems (see, for example, Chemistry and Industry (1990)600-608).

The suitability of the novel substances in communications technology, inelectrooptical modulators (eg. Mach-Zehnder interferometer), in opticalswitches, in frequency mixing or in waveguides should be particularlyemphasized here.

The novel methine dyes of the formula I are also suitable in anadvantageous manner, for example, for dyeing or printing textilematerials. These are, for example, fibers or fabrics, in particular ofpolyesters, but also of cellulose esters or polyamides, or blendedfabrics composed of polyesters and cellulose fibers or wool.

Furthermore, the novel methine dyes of the formula I are advantageouslysuitable for dyeing polymers in bulk, for use in electrophotography asdyes for electrostatic toners or as dyes for thermal transfer.

The Examples which follow illustrate the invention.

EXAMPLE 1

a) 154 g (1.0 mol) of chloroacetophenone were introduced into 800 ml ofethanol. Subsequently, 76 g (1.0 mol) of ammonium thiocyanate wereadded, and the mixture was boiled for 4 h. It was subsequently cooled to20° C., and 66 g (1.0 mol) of malononitrile and 101 g (1.0 mol) oftriethylamine were added. The reaction mixture was stirred at 20° C. for12 h and then poured into 2000 ml of water, the mixture was acidified topH 4 with glacial acetic acid, and the resulting precipitate wasfiltered off with suction. The product was dried at 50° C. under reducedpressure to obtain 131 g of the compound of the formula ##STR9##

C₁₂ H₇ N₃ S (225) calc.: C 64.00 H 3.13 N 18.67 S 14.0 found: C 63.70 H3.33 N 18.50 S 13.91

b) 1.61 g (0.1 mol) of 4-dimethylaminocinnamaldehyde and 2.25 g (0.01mol) of the compound obtained under a) were heated at 80° C. in 35 ml ofacetic anhydride for 2 h. After cooling to 20° C., the mixture wasstirred at this temperature for a further 12 h. The resulting dye wasfiltered off with suction, washed with isopropanol and dried at 50° C.under reduced pressure to obtain 2.05 g of the compound of the formula##STR10##

C₂₃ H₁₈ N₄ S (382) calc.: C 72.23 H 4.74 N 14.65 S 8.38 found: C 72.10 H4.63 N 14.34 S 8.10

EXAMPLE 2

Example 2 was carried out as Example 1 but using4-diethylaminocinnamaldehyde in place of the dimethylamino compound toobtain 3.30 g of the compound of the formula ##STR11##

C₂₅ H₂₂ N₄ S (418) calc.: C 71.78 H 5.26 N 13.39 found: C 71.58 H 5.44 N13.28

EXAMPLE 3

The procedure was as in Example 1 but using as aldehyde component thecompound of the formula ##STR12## to obtain 3.08 g of the compound ofthe formula ##STR13##

C₂₉ H₂₆ N₄ O₂ S (495) calc.: C 70.42 H 5.30 N 11.33 O 6.47 found: C70.63 H 5.43 N 11.53 O 6.60

EXAMPLE 4

The procedure was as in Example 1 but using as aldehyde component thecompound of the formula ##STR14## to obtain 3.5 g of the compound of theformula ##STR15##

EXAMPLE 5

a) 3.41 g (0.02 mol) of ω-chloro-4-hydroxyacetophenone were dissolved in100 ml of chloroform and admixed with 2 g of pyridine and 20 mg of4-dimethylaminopyridine. 6 g (0.02 mol) of methacrylic anhydride werethen added dropwise at 20° C. Thereafter the mixture was stirred at 50°C. for a further 1 h and then poured onto 500 g of water for hydrolysis.The organic phase was separated off, washed with water and then driedover potassium carbonate. Concentrating the organic phase under reducedpressure at 50° C. left the product as a solid residue, which waspurified by recrystallization with ethanol to leave 3.08 g of thecompound of the formula ##STR16##

calc.: C 60.50 H 4.62 O 20.17 found: C 60.45 H 4.70 O 20.07

b) 0.96 g (4 mmol) of the compound obtained under a) were introducedinto a mixture of 10 ml of ethanol and 0.3 g (4 mmol) of ammoniumthiocyanate. 20 mg of phenothiazine were added as stabilizer. Themixture was then heated at 50° C. for 4 h. Thereafter it was cooled downto 20° C., and the resulting residue was filtered off with suction andwashed with water. The product was dried under reduced pressure at 50°C. to leave 0.81 g of the compound of the formula ##STR17##

calc.: C 62.65 H 4.42 N 5.62 found: C 62.42 H 4.38 N 5.55

c) 0.76 g (2.9 mmol) of the compound obtained under b) were suspended in10 ml of ethanol and admixed with 20 mg of phenothiazine and 0.2 g ofmalononitrile. The mixture was then heated to 45° C. and admixed with0.38 ml of triethylamine. After 1 h the mixture was cooled down to 20°C. and stirred at that temperature for 10 h. Thereafter the batch waspoured onto 300 ml of dilute aqueous acetic acid, the mixture wassubsequently stirred for 15 min, and the resulting precipitate wasfiltered off with suction. The product was washed neutral with 2,000 mlof water and dried under reduced pressure at 40° C. to leave 0.6 g ofthe compound of the formula ##STR18##

calc.: C 62.12 H 3.56 N 13.60 O 10.36 found: C 62.28 H 3.50 N 13.46 O10.35

d) 2.03 g (0.01 mol) of 4-diethylaminocinnamaldehyde and 3.09 g (0.01mol) of the compound obtained under c) were briefly heated to the boilin 30 ml of acetic anhydride. Thereafter the mixture was immediatelycooled down to 0° C. and stirred at that temperature for 4 h. Theresulting precipitate was filtered off with suction and washed with alittle cold methanol to leave 3.5 g of the compound of the formula##STR19##

calc.: C 70.44 H 5.26 N 11.34 found: C 70.32 H 5.30 N 11.19

EXAMPLE 6

a) 12.8 g (0.075 mol) of 4-hydroxy-ω-chloroacetophenone were heated with14 ml of acetic anhydride and 1 ml of concentrated sulfuric acid to 100°C. for 14 h. After the reaction solution had been cooled down, it waspoured onto 200 ml of ice-water and the resulting solid was filtered offwith suction to leave 14.8 g of the compound of the formula ##STR20##

C₁₀ H₉ O₃ Cl (212,5) calc.: C 56.47 H 4.26 O 22.59 found: C 56.40 H 4.31O 22.80

b) 10,4 g (0.044 mol) of the compound described under a) were heatedwith 50 ml of ethanol and 2.9 g (0.044 mol) of malononitrile to 40° C.The mixture was then cooled down to 20° C. and mixed with 5.5 ml oftriethylamine. It was then stirred at 20° C. for 12 h, and acidified topH 4 with glacial acetic acid, and the resulting solid was filtered offwith suction. Washing with water and drying at 50° C. under reducedpressure left 10 g of the compound of the formula ##STR21##

C₁₄ H₉ N₃ O₂ S (283) mp.: >250° C. calc.: C 59.36 H 3.18 N 14.84 S 11.31found: C 59.40 H 3.51 N 14.58 S 11.22

c) 28.3 g (0.1 mol) of the compound described under b) were heated with23.8 g (0.1 mol) of 4-dibutylaminobenzaldehyde to the boil in 130 ml ofacetic anhydride for 0.5 h. After cooling, the mixture was stirred at20° C. for 12 h. The resulting dye was filtered off with suction, washedwith 10 ml of xylene and 50 ml of methanol and dried at 50° C. underreduced pressure to leave 32 g of the dye of the formula ##STR22##

C₂₉ H₃₀ N₄ O₂ S (498) mp.: 197° C.

d) 32 g (0.064 mol) of the dye described under c) were dissolved at 20°C. in a mixture of 400 ml of ethanol, 140 ml of water and 16.6 g (0.12mol) of potassium carbonate. The mixture was then heated to the boil for1 h. After cooling, the solvent was removed under reduced pressure, andthe residue was suspended in 300 ml of water and acidified to pH 2.5with 0.1N hydrochloric acid. The resulting precipitate was filtered offwith suction, washed with 200 ml of water and dried at 50° C. underreduced pressure to leave 28 g of the dye of the formula ##STR23##

C₂₇ H₂₈ N₄ OS (456) calc.: C 71.10 H 6.14 N 12.28 O 3.51 found: C 69.5 H6.32 N 12.10 O 5.83

EXAMPLE 7

a) 5.6 g (0.02 mol) of the compound described under 1b) and 3.5 g (0.02mol) of 4-dimethylaminocinnamaldehyde were heated to 100° C. in 20 ml ofacetic anhydride for 1 h. After cooling, the resulting precipitate wasfiltered off with suction and washed with 20 ml of xylene and 10 ml ofmethanol. Drying at 50° C. under reduced pressure left 2.4 g of the dyeof the formula ##STR24## b) 1.2 g (2.7 mmol) of the dye described undera) were heated to the boil in a mixture of 20 ml of ethanol, 6 ml ofwater and 0.7 g of potassium carbonate for 1 h. After cooling, thesolvent was distilled off under reduced pressure. The residue wassuspended in 50 ml of water and acidified with 0.1N hydrochloric acid topH 2.5. The resulting precipitate was filtered off with suction, washedwith 50 ml of water and dried at 50° C. under reduced pressure to leave0.95 g of the dye of the formula ##STR25##

C₂₃ H₁₈ N₄ OS (398) calc.: C 69.35 H 4.52 N 14.07 found: C 69.10 H 4.63N 14.02

The dyes listed in the following Table 1 were obtained similarly to theabove examples.

                                      TABLE 1                                     __________________________________________________________________________    Example No.                                                                          Formula                                                                __________________________________________________________________________            ##STR26##                                                             9                                                                                     ##STR27##                                                             10                                                                                    ##STR28##                                                             11                                                                                    ##STR29##                                                             12                                                                                    ##STR30##                                                             13                                                                                    ##STR31##                                                             14                                                                                    ##STR32##                                                             15                                                                                    ##STR33##                                                             16                                                                                    ##STR34##                                                             17                                                                                    ##STR35##                                                             18                                                                                    ##STR36##                                                             19                                                                                    ##STR37##                                                             20                                                                                    ##STR38##                                                             21                                                                                    ##STR39##                                                             22                                                                                    ##STR40##                                                             23                                                                                    ##STR41##                                                             24                                                                                    ##STR42##                                                             25                                                                                    ##STR43##                                                             __________________________________________________________________________

The method described in Z. Naturforschung 20a (1965) 1441-1471 was usedto determine the absorption maxima of each of the individual dyes indioxane and dimethyl sulfoxide (DMSO), and then the solvatochromic shift.increment.v cm⁻¹ ! was determined.

The results of the measurements are listed in the following Table 2.

                  TABLE 2                                                         ______________________________________                                               λ.sub.max                                                                             λ.sub.max                                        Dye    (dioxane)      (DMSO)   Δv                                       Nr.     nm!            nm!      cm.sup.-1 !                                   ______________________________________                                        1      636            746      2318                                           2      647            763      2350                                           3      645            765      2419                                           14     647            763      2350                                           15     645            762      2380                                           ______________________________________                                    

The suitability of the dyes according to the invention in nonlinearoptics is furthermore shown by the determination of thehyperpolarizability (β₀) of the dye described in Example 2. Thehyperpolarizability was determined by an electrooptical absorptionmeasurement. The complete theory on this measurement method is to befound in Chem. Phys. 173 (1993) 305-314, Chem. Phys. 173 (1993) 99-108and J. Phys. Chem. 96 (1992) 9724-9730. Besides the hyperpolarizability(β₀) the relevant variable important for polymeric nonlinear opticalsystems is μ_(g) β₀ (μ_(g) =dipole moment in the ground state) becauseμ_(g) β₀ is directly proportional to the 2nd order susceptibility. Themeasured values are compared with those for dimethylaminonitrostilbene(DMANS) in the following Table 3.

                  TABLE 3                                                         ______________________________________                                        Dye        β.sub.0  10.sup.-50 Cm.sup.3 V.sup.-2 !                                              μ.sub.g β.sub.0  10.sup.-80 C.sup.2                                   m.sup.4 V.sup.-2 !                                     ______________________________________                                        Dye No. 2  95          4170                                                   DMANS      33          820                                                    ______________________________________                                    

The relevant variable μ_(g) β₀ for the methine dye according to theinvention is 5 times that for the compound disclosed in the literature,and this impressively underlines the suitability of the novel dyes innonlinear optics.

We claim:
 1. A methine dye of the formula I ##STR44## where R is##STR45## where W is hydrogen, C₁ -C₆ -alkanoyl, acryloyl ormethacryloyl, X is a radical of the formula CQ¹, CH═CQ¹ --CH,CH═CH--CH═CH--CH, ##STR46## where Q¹ is hydrogen, C₁ -C₄ -alkyl,chlorine or bromine and Q² is hydrogen or C₁ -C₄ -alkyl, andY is a adye-imparting group containing a moiety selected from the groupconsisting of aniline, aminonaphthalene, indole, aminoquinoline andaminothiophene.
 2. A methine dye as claimed in claim 1, wherein themoiety in Y is aniline, aminonaphthalene or aminoquinoline.
 3. A methinedye as claimed in claim 1, wherein X is a radical of the formula CH,CH═CH--CH or CH═CH--CH═CH--CH.
 4. A methine dye as claimed in claim 1,wherein the moiety in Y is aniline.
 5. A thiazole derivative of theformula IVa ##STR47## where W is hydrogen, C₁ -C₆ -alkanoyl, acryloyl ormethacryloyl.
 6. A process for dyeing a substrate comprising applyingthe methine dye of claim 1 to said substrate to effect dyeing thereof.